System for transmitting interacting data between neighboring bss via ms and method thereof

ABSTRACT

The present invention provides a system for transmitting interacting data between neighboring BSs via a MS and a method thereof The system comprises a first BS which transmits the interacting data to the MS, and a MS which receives the interacting data from the first BS and transmits the received interacting data to a second BS that neighbors to the first BS. The invention also provides a communication system and a method thereof, wherein a MS communicates with a first BS using an established first communication channel, and the MS to communicates with the second BS using an established second communication channel. The system of the invention uses a MS within the overlapped coverage area of neighboring BSs to perform transmission of interacting data such as control information for coordination, so as to reduce latency required for interacting data transmission between neighboring BSs. Compared to legacy BS coordination via a backbone, the BS coordination via a MS of the invention is predictable and requires less latency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of wireless communications,and in particular to a system for transmitting interacting data betweenneighboring BSs (Base Stations) via a MS (Mobile Station) and a methodthereof. This invention also relates to a communication system and amethod thereof.

2. Description of the Prior Art

IMT-Advanced next generation mobile networks have raised requirements onsystem capability. Some standard groups or organizations are activelydeveloping drafts to meet the requirements, and expecting their draftsto be candidates for consideration in the IMT-Advanced evaluationprocess. IEEE802.16m task group which was recently launched aims to makesome amendment to IEEE Std 802.16, in order to provide an advanced airinterface with performance improvements for operation in licensed bands.It targets the cellular layer requirements of IMT-Advanced nextgeneration mobile networks.

With the technical development targeting IMT-Advance, neighboring BSsare required to collaborate with each other with adoption of some newtechniques. Neighboring BS coordination for control information exchangeis getting more and more important and frequent, which is performed suchthat BS exchanges some control information, channel information, orrequest/response messages with its neighboring BSs for collaboration.This coordination is necessary for lots of functionalities in mobilecommunications, such as fast handover, network MIMO (Multi-InputMulti-Output), interference cancellation, fragment resource reuse, MBSetc. For example, during a handover the serving BS has to negotiate withneighboring BSs for a potential candidate of Target BS, to check if anyof the neighboring BSs would like to accept a moving MS or not. FIG. 1is a schematic diagram of neighboring BS coordination for controlinformation exchange according to the conventional method.

During the handover, the serving BS sends to a neighboring BS apre-notification request including MS context configuration information,and the neighboring BS sends back a response including service levelpredication with estimated HO time and HO optimization. Upon thecompletion of the handover, the target BS also sends to the old servingBS a notification indicating that it is now hosts the MS in order thatthe old serving BS may release all MS resources. Another example isneighboring BS coordination for interference cancellation, or fragmentresource reuse. Some time-frequency scheduling information should beexchanged and shared among neighboring BSs for the purpose ofinterference cancellation or resource reuse.

An example of data information exchange between neighboring BSs is thata BS transmits data to be downlink transmitted to a MS to a neighboringBS via a backbone. Such technique can be applied to MBS (MulticastBroadcast Service).

The latency requirement has been raised for neighboring BS controlcoordination. Less latency can decrease possible service interruptionand improve the performance.

Existing neighboring BS coordination for control information exchange istransmitted via a backbone. For example, neighboring BS negotiationmessage pre-notification request/response for handover are exchanged viathe backbone. The backbone is suitable for massive data transmission dueto its higher transmission capability. However, the coordination messagetransmission routing and latency are highly dependent on the BSs'locations and on what clusters they belong to. The transmission latencyis thus unpredictable. It may last a longer time period if the involvedBSs do not belong to a single cluster. A cluster is typically definedsuch that neighboring BSs is subordinate to the same controller. Forexample, if BSs belong to the same WAC in WiMAX, or belong to the sameRNC in 3GPP, they belong to the same cluster.

Exemplified in WiMAX network, the routing and latency are different forneighboring BS control information exchange, depending on whether thecoordinated BSs belong to the same WAC or not. FIG. 2( a) illustratescontrol information exchange between BSs subordinate to a single WAC.The control messages are exchanged and forwarded via the common WAC, andthus subjected to less latency.

On the other hand, FIG. 2( b) illustrates control information exchangebetween BSs subordinate to different WACs. For the purpose ofcoordination, BS1 first transmits control information to its own WAC1.Then, the information may be forwarded by routers from the WAC1 to WAC2,and may also experience IP encapsulation/encapsulation. When theinformation reaches the WAC2 to which the neighboring BS is subordinate,the WAC2 continues to forward it to the destination BS2. As can be seenfrom this procedure, the total latency may include transmitting delay,routing/switching delay, and possibly encapsulation/encapsulation delay.Consequently, the total latency for control information transmission isunpredictable.

In summary, the latency for control information exchange betweenneighboring BS via a backbone is unpredictable, depending on neighboringBSs' locations and on which cluster they belong to. It may require alonger time delay if the involved BSs belong to different clusters (i.e.the BSs belong to different WACs in WiMAX).

With tougher requirements on time delay for fast handover, network MIMO,interference cancellation, etc., neighboring BS coordination is gettingmore important and frequent.

SUMMARY OF THE INVENTION

Currently, there is no real direct BS-BS connection for coordination. Tosolve the above problems, the present invention is provided to implementa direct BS-BS connection via a MS. According to this invention, asystem for transmitting interacting data between neighboring BSs via aMS and a method thereof are provided. With the system and method, theinvention can enable transmission of interacting data such as controlinformation for BS coordination, and a bi-directional coordination. Witha MS within the overlapped coverage area of the neighboring BSsperforming merely simple transmission operation, the latency of controlinformation exchange can be reduced and become predictable. The BSs isin charge of establishment of control channel and transmission. Comparedto the legacy BS coordination via a backbone, the interacting datatransmission for BS coordination via a MS is predictable and lesslatency.

According to a first aspect of the present invention, a system fortransmitting interacting data between neighboring BSs via a MS isprovided, comprising: a first BS which transmits the interacting data;and a MS which receives the interacting data from the first BS andtransmits the received interacting data to a second BS that neighbors tothe first BS.

According to a second aspect of the present invention, a method oftransmitting interacting data between neighboring BSs via a MS isprovided, comprising: transmitting from a first BS to a MS theinteracting data; and transmitting from the MS to a second BS thatneighbors to the first BS the interacting data received from the firstBS.

According to a third aspect of the present invention, a communicationsystem is provided, comprising: a MS; a first BS which establishes afirst communication channel used for the communication with the MS; anda second BS which establishes a second communication channel used forthe communication with the MS; wherein the MS communicates with thefirst BS using the established first communication channel andcommunicates with the second BS using the established secondcommunication channel.

According to a fourth aspect of the present invention, a communicationmethod is provided, comprising: communicating by a MS with a first BSusing an established first communication channel; and communicating bythe MS with a second BS using an established second communicationchannel.

According to a fifth aspect of the present invention, a MS fortransmitting interacting data between neighboring BSs is provided,comprising: a control unit which controls the transmission ofinteracting data which is received from a first BS; a receiving unitwhich receives the interacting data from the first BS; and a sendingunit which transmits the interacting data received from the first BS toa second BS.

According to a sixth aspect of the present invention, a BS interactingwith neighboring BS is provided, comprising: a BS coordination unitwhich controls the transmission of interacting data between neighboringBSs to a MS; a BS transmitting unit which transmits interacting data tothe MS; and a BS receiving unit which receives data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of neighboring BS coordination for controlinformation exchange according to the conventional method.

FIG. 2 a shows control information exchange between neighboring BSssubordinate to a single WAC.

FIG. 2 b shows control information exchange between BSs subordinate todifferent to WACs.

FIG. 3 a shows a system for transmitting interacting data betweenneighboring BSs via a MS according to the present invention.

FIG. 3 b shows a flowchart for a method of transmitting controlinformation for neighboring BS coordination via a MS according to thepresent invention.

FIG. 4 a is a schematic block diagram of a BS according to the presentinvention.

FIG. 4 b is a schematic block diagram of a MS according to the presentinvention.

FIG. 5 is an example of a frame structure for channel assignmentaccording to the present invention.

FIG. 6 is a schematic diagram of bi-directional channels between MS andBS according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings, throughout whichlike components are denoted with like symbols or numbers. In thefollowing description of the present invention, a detailed descriptionof known functions and configurations incorporated herein will beomitted, otherwise it may obscure the subject matter of the presentinvention.

The total latency for control information transmission is notpredictable due to the conventional wired transmission of the controlinformation between the neighboring BSs. Therefore, there may be a longlatency. This is unacceptable to communications which require lesslatency.

This invention provides a scheme of BS-BS data transmission via a MS.That is, interacting data between neighboring BSs is transmitted via aMS. The interacting data comprises data to be transmitted betweenneighboring BSs, such as user data (for example, data to be transmittedto a MS within the coverage area of the neighboring BSs, or data sent bya MS within the coverage area of the neighboring BSs), and controlinformation for neighboring BS coordination. FIG. 3 a shows a system fortransmitting interacting data between neighboring BSs via a MS accordingto the present invention. Referring to FIG. 3 a, a MS is located withinthe overlapped coverage of two neighboring BSs. BS1 first sendsinteracting data for its neighboring BSs to the MS, and the MS thentransmits the interacting data to one of the neighboring BSs, BS2. Forexample, the BS1 sends to the MS control information for neighboring BScoordination. Then, the MS forwards the received control information tothe BS2. One skilled in the art can appreciate that there can be one ormore BS2. The transmission of the interacting data of neighboring BSs,e.g., control information exchange, is performed via a MS, instead of amain backbone that has an unpredictable routing and a long latency.Therefore, the total latency of data transmission can be decreased.

FIG. 4 a is a schematic block diagram of a BS according to thisinvention. The BS comprises a transmitting unit 41, a receiving unit 42,a neighboring BS coordination unit 44 and a BS control unit 43. Thetransmitting unit 41 transmits data, such as control information forneighboring BS coordination, to a MS within the coverage area of thecell the BS belongs to. The receiving unit 42 receives data sent from aMS within the coverage area of the cell or data sent from neighboringBSs. The BS control unit 43 controls the transmitting/receiving andprocessing of data and also controls the MS within the coverage area.The neighboring BS coordinating unit 44 identifies the MS within theoverlapped coverage area of the BS and its neighboring BS, and sendsinteracting data for the neighboring BS to the identified MS. Theneighboring BS coordinating unit 44 is also used to set up acommunication channel. The structure of the BS2 is similar to that shownin FIG. 4 a, and thus the description thereof is omitted.

FIG. 4 b is a schematic block diagram of a MS according to thisinvention. Referring to FIG. 4 b, the MS comprises a transmitting unit401, a receiving unit 402, a MS first control unit 403 and a MS secondcontrol unit 404. The transmitting unit 401 and the receiving unit 402are used to transmit/receive data, respectively The MS first controlunit 403 is used to process received/transmitted data (if necessary).The MS second control unit 404 transmits interacting data, such ascontrol information for neighboring BS coordination, between the BS andits neighboring BS via a channel to the neighboring BS, or by othermethods, such as MAP IE, data burst etc. The MS does not process theinteracting data for the neighboring BS from the BS1. It simplytransmits the interacting data as it is to the BS2. The interacting datafrom the BS1 is transparent to the MS.

This invention enables the transmission of interacting data betweenneighboring BSs via a MS, and the interacting data comprises data to betransmitted between the neighboring BSs, such as user data (for example,data to be transmitted to a MS within the coverage area of theneighboring BS, or data sent by a MS within the coverage area of theneighboring BS) and control information for neighboring BS coordination.In the following paragraphs, a flow of forwarding control informationwill be described with reference to FIGS. 3 a, 3 b, 4 a, and 4 b, bytaking an example of forwarding control information for neighboring BScoordination via a MS.

Referring to FIG. 3 b, at S31, the neighboring BS coordination unit 44of BS1 and the neighboring BS coordination unit of BS2 identify a MSwithin an overlapped coverage area of the two neighboring BSs, BS1 andBS2, for forwarding control information for coordination, wherein theBS2 is a neighbor to the BS1. Generally, most of neighboring BScoordination exchange is conducted for the MS (e.g. for MS handover)within the overlapped coverage. Although in this example only one MS isshown, it can be understood that more than one MS may be adopted.

Then, at S32, the neighboring BS coordination unit 44 of BS1 sets up achannel between the BS1 and the MS. The neighboring BS coordination unitof BS2 sets up a channel between the MS and the BS1.

Specifically, after the MS within the overlapped coverage area of theneighboring BSs is identified, BS1 sets up a channel between BS1 and theMS for communication, and BS1 transmits a message to the BS2 to notifyBS2 to set up a channel with the MS. BS2 sets up a channel forcommunicating with the MS, when the message from the BS1 is received.The channels between BS1 and MS and between MS and BS2 can besingle-directional channel or bi-directional channel, and the channelscan be an allocated burst, a dedicated control channel, a CDMA controlchannel, etc.

Alternatively, a common channel can be established between a pluralityof BS2 and a MS. The common channel refers to a channel shared by aplurality of BS2 and between the plurality of BS2 and a MS. At first,the BS1 assigns one resource block, and notifies a plurality of BS2(such as neighboring BS2) to reserve the same resource block as thatassigned by the BST. Thus, the plurality of BS2 reserve the sameresource block as a common channel. The MS may broadcast controlinformation for neighboring BS coordination in uplink via the commonchannel shared by the plurality of BS2. The MS transmits the controlinformation in uplink via the common channel, and the controlinformation is received by the plurality of BS2.

For example, a CDMA control channel is built such that sometime-frequent resource is reserved for control information transmissionfor one or more MSs within the overlapped coverage area of the BS1 andBS2, and these MSs may use pre-coded CDMA for signaling. Alternatively,a MS is also allowed to use a neighboring BS2's reserved CDMA controlchannel to communicate with the BS2. CDMA control channel can be usedfor both downlink and uplink.

A plurality of BSs can be notified of the assigned channel resource, sothat they can monitor the common channel and receive the controlinformation forwarded by the MS. Moreover, it is obvious that otherchannels can also be used for transmitting control information forneighboring BS coordination via a MS.

Since single-directional or bi-directional channels are set up betweenthe neighboring BSs and the MS, respectively, or since a pre-assignedcommon channel is used, the MS can maintain the channels with theneighboring BS1 and BS2 simultaneously. Therefore, the MS cancommunicate with the BS1 and BS2 simultaneously without performing ahandover process comprising the MS's registration to the BS2. Moreover,there is no need for forwarding the control information for neighboringBS coordination via a backbone, and thus latency required fortransmitting the control information can be reduced.

FIG. 6 is a schematic diagram of bi-directional channels between the MSand the BSs according to the present invention. Assume that the MS isregistered and subordinate to BS1, and downlink/uplink communicationsbetween the MS and BS2 occupy the CDMA control channel assigned by BS2.This control channel is initially assigned for signaling control betweenBS2 and MS s within its coverage.

In the present invention, the MS is allowed to use the CDMA controlchannel of the neighboring BS2 to forward the control information forneighboring BS coordination. FIG. 5 is an example of a frame structurefor channel assignment. In the frame structure, bi-directional channelsare assigned. This is merely an example, and this invention may use anyappropriate channels other than the CDMA control channel.

At S33, the transmitting unit 41 of BS1 transmits the controlinformation for neighboring BS coordination to the MS. When a BS hascontrol information to be exchanged, the BS can transmit the controlinformation to the MS via an assigned channel or by other methods, suchas MAP IE, data burst, etc.

At S34, the MS second control unit 404 of the MS receives the controlinformation by the receiving unit 402, and forwards the controlinformation to the BS2 via an established channel. The second controlunit 404 forwards the control information as it is to the neighboringBS2, without any processing on the control information.

The BS1 may transmit to the MS control information that is encrypted.The control information is transparent to the MS. The MS does not decodethe control information to get data contents after receiving theencrypted information. It simply forwards the received information as itis from the BS1 to the neighboring BS2. Depending on the processingcapability of the MS, the MS may forward the control information withinone frame.

The BS2 receives the control information from the MS. After a channelfor communication between the MS and the BS2 is set up, the BS2 knowsthe existence of the channel and monitors the channel. The BS2 receivesthe control information when it is transmitted via the monitoredchannel.

With the MS moving, the channel condition changes, and BS determineswhether a channel is required for information exchange. If it is notrequired, the BS may release the channel. Further, the BS may update thechannel according to changes in channel condition.

Although the above is illustrated by an example of forwarding thecontrol to information for neighboring BS coordination via a MS, it isunderstood that interacting data between neighboring BSs can also betransmitted via a MS in the same way. The MS does not process thereceived interacting data for neighboring BSs. Instead, it simplytransmits the interacting data as it is from the BS1 to the BS2.

Since single-directional or bi-directional channels are set up betweenBS1 and the MS as well as between the MS and BS2, the MS cancommunicates with BS1 by means of any conventional method whilecommunicating with the BS2 via the established channel between them,i.e., communicating with the BS2 without performing handover. Moreover,MS may transmit data of itself to the BS2 besides the interacting dataof the neighboring BSs. The data of the MS itself can be, for example,channel measurement result, handover request and MS uplink data. BS2 canalso transmit data to the MS for communication. Alternatively, the MSmay transmit data to a plurality of BSs via an assigned common channel.

The present invention can be applied to transmission of interacting datawith higher time-delay requirement, since it enables to transmit theinteracting data of neighboring BSs via a MS. No backbone is required toperform transmission of interacting data between neighboring BSs, andthus the latency of interacting data transmission is reduced. Comparedwith the conventional BS coordination via a backbone, the BScoordination via a MS is predictable and has less latency, and thecommunication performance between neighboring BSs is enhanced.

While specific embodiments of the present invention have beenillustrated and described, it can be understood that the invention isnot limited to the description disclosed herein. It will be apparent tothose skilled in the art that various modifications, changes, andvariations may be made to the present invention disclosed herein withoutdeparting from the spirit and scope of the invention.

1. A system for transmitting interacting data between neighboring BaseStations (BSs) via a Mobile Station (MS), comprising: a first BS whichtransmits the interacting data; and a MS which receives the interactingdata from the first BS and transmits the received interacting data to asecond BS that neighbors to the first BS.
 2. The system of claim 1,wherein the interacting data between neighboring BSs comprises controlinformation for neighboring BS coordination.
 3. The system of claim 1,wherein the first BS transmits the interacting data to the MS within theoverlapped coverage area of the first BS and the second BS via anestablished channel; the MS transmits the interacting data received fromthe first BS to the second BS via an established channel between the MSand the second BS.
 4. The system of claim 3, wherein the channel betweenthe first BS and the MS or/and the channel between the second BS and theMS is/are a single-directional or bi-directional channel; the channel isone of an allocated burst, a dedicated control channel, a common channeland a CDMA control channel.
 5. (canceled)
 6. (canceled)
 7. (canceled) 8.(canceled)
 9. The system of claim 63, wherein the MS broadcasts theinteracting data from the first BS to a plurality of second BSs via acommon channel shared by the plurality of the second BSs as an uplink.10. A method of transmitting interacting data between neighboring BaseStations (BSs) via a Mobile Station (MS), comprising: transmittinginteracting data from a first BS to a MS; and transmitting theinteracting data received from the first BS from he MS to a second BSthat neighbors to the first BS.
 11. (canceled)
 12. The method of claim10, wherein the first BS transmits the interacting data to the MS withinthe overlapped coverage area of the first BS and the second BS via anestablished channel; the MS transmits the interacting data received fromthe first BS to the second BS via an established channel between the MSand the second BS.
 13. The method of claim 12, wherein the channelbetween the first BS and the MS or/and the channel between the second BSand the MS is/are a single-directional or bi-directional channel; thechannel is one of an allocated burst, a dedicated control channel, acommon channel and a CDMA control channel.
 14. (canceled)
 15. (canceled)16. (canceled)
 17. (canceled)
 18. The method of claim 13, wherein thecommon channel is established by: allocating by the first BS a resourceblock and notifying it to a plurality of second BSs; and reserving byeach of the plurality of second BSs a resource block identical to theallocated resource block, as the common channel.
 19. (canceled)
 20. Acommunication system, comprising: a MS; a first BS which establishes afirst communication channel for communication with the MS; and a secondBS which establishes a second communication channel for communicationwith the MS; wherein the MS communicates with the first BS using theestablished first communication channel, and communicates with thesecond BS using the established second communication channel; the MSmaintains the first communication channel and the second communicationchannel simultaneously, so that the MS communicates with both of thefirst BS and the second BS without any handover.
 21. (canceled)
 22. Thesystem of claim 20, wherein the second communication channel is a commoncommunication channel, and data transmitted by the MS via the commonchannel are received by a plurality of second BSs.
 23. A communicationmethod, comprising: communicating by a MS with a first BS using anestablished first communication channel; and communicating by the MSwith a second BS using an established second communication channel; theMS maintains the first communication channel and the secondcommunication channel simultaneously, so that the MS communicates withboth of the first BS and the second BS without any handover. 24.(canceled)
 25. The method of claim 23, wherein the second communicationchannel is a common channel, and data transmitted by the MS via thecommon channel is received by a plurality of second BSs, and the commonchannel is established by: allocating by the first BS a resource blockand notifying it to a plurality of second BSs; and reserving by each ofthe plurality of second BSs a resource block identical to the allocatedresource block, as the common channel.
 26. A Mobile Station (MS) fortransmitting interacting data between neighboring Base Stations (BSs),comprising: a control unit which controls transmission of interactingdata received from a first BS; a receiving unit which receives theinteracting data from the first BS; and a transmitting unit whichtransmits to a second BS the interacting data received from the firstBS.
 27. A Base Station (BS) for transmitting interacting data between itand its neighboring BS, comprising: a BS coordination unit whichcontrols transmission of interacting data to a MS; a BS transmittingunit which transmits the interacting data to the MS; and a BS receivingunit which receives data.